<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <script>
        //数据类型
        // let hd = "3";
        // console.log(typeof hd);
        // let arr = [1, 2, 3];  //array 也object
        // console.log(typeof arr);
        // let obj = {};
        // console.log(typeof obj);
        // function run() { };
        // console.log(typeof run);

        // console.log(typeof cc);
        // let aa; //只定义没有值也是undefined
        // console.log(typeof aa);

        // console.log(aa == 'undefined');

        let hd = [];
        let hdcms = {};
        console.log(typeof hd);
        // hd.prototype;//原型链
        // console.log(hd.prototype);
        console.log(hd instanceof Array);//原型链是否有Array这个属性
        console.log(hdcms instanceof Object);

        function User() {

        }
        let wfj = new User();
        console.log(wfj instanceof User); //原型链是否有User这个属性
        console.log(wfj instanceof Object); //原型链是否有Object这个属性
        // instanceof 更加细致 typeof 基本的

    </script>
</body>

</html>